1. Field Of The Invention
The present invention relates generally to electrophotography and more particularly to improvements in developing an image on an electrophotographic element.
2. Description Of The Prior Art
In electrophotography, it is common to apply a uniform electrostatic charge to the surface of a photoconductive layer. The charge is then selectively dissipated in a pattern by exposing the surface to a light image. The resulting pattern of charges produces an electrostatic latent image on the photoconductive layer, which is rendered visible by applying to it electrostatically charged toner particles which adhere to the surface of the photoconductive layer by electrostatic attraction. A permanent visible image can be obtained by using toner particles which can be heat fused to the photoconductive layer and subjecting them to a heat application step.
In the conventional developing method using liquid developer, which is a liquid carrier for finely divided electrostatic particles such as carbon particles, the image-exposed film is dipped in the liquid developer to produce a visible image corresponding to the latent image thereon. While this method of developing is satisfactory for some types of systems and film, it is not satisfactory for the type of system in which imaging and developing takes place automatically within a single apparatus, such as the microphotographic copying machine described in commonly assigned co-pending application Ser. No. 349,452 now U.S. Pat. No. 3,972,610. In that microphotographic copying machine, data from successive documents is sequentially recorded on individual frames of a multi-frame microfiche. Because it is desirable to image and develop each frame quickly before repeating the process for the next frame, the process for developing the images must be one which can be carried out quickly and conveniently to a microfiche fixed within a holder within the reproduction apparatus. Additionally, the developing system must be capable of quickly applying the correct amount of developer, or toner particles (which are preferably suspended in a liquid carrier), to the imaged area of the film and removing the toner particles from the film without permitting leakage of the toner particles into the interior of the reproduction apparatus. The system must also be capable of quickly evaporating any of the toner carrier liquid remaining on the film to immobilize the toner particles remaining on the film and prevent smearing of the toned imaged.
Therefore, it is an object of the invention to provide a method and apparatus for quickly applying a measured quantity of liquid toner to an imaged area of a film without permitting leakage of the liquid toner beyond the imaged area of the film. A further object of the invention is to quickly evaporate residual toner carrier liquid remaining on the film after toning. And a further object of the invention is to provide a method and apparatus for accomplishing the above objects while the film is held in a carrier within a microphotographic reproduction apparatus.